In photographic processing apparatus, elastomer covered rollers are employed to transport film and photographic paper through tanks of processing solutions. Presently, these rollers are manufactured by transfer molding a thermosetting elastomeric compound on a shaft such as stainless steel. The shaft is prepared by roughing the surface, for example by sand blasting, and applying a solvent based primer adhesive to the surface of the shaft. After air drying for approximately 30 minutes, a main solvent based adhesive is applied to the shaft and air dried for approximately 30 more minutes. The shaft is then placed in a thermal compression mold, surrounded by uncured elastomer, and baked for example at 350.degree. for 30-40 minutes to cure (vulcanize) the elastomer and adhesive system. After cooling, the elastomer covered roller is removed from the mold, and ground to finish tolerance. This many step process is labor intensive and time consuming (and hence expensive) and employs environmentally undesirable solvent based adhesives.
In addition, when the elastomeric surface of such a roller experiences wear or is damaged, the roller including the shaft is discarded.
An alternative method of manufacturing elastomeric covered rollers, called interference fit manufacturing employs a preformed tube of elastomeric material, having an inside diameter less than the diameter of the shaft. The tube is placed on the shaft by introducing compressed air into one end of the tube while the shaft is introduced into the other end. The compressed air expands the elastomeric tube sufficiently to enable the shaft to be introduced. When the compressed air is removed, the elastomeric tube tightly grips the shaft without the need for pretreating the shaft or applying any adhesives. Such rollers can be manufactured to finish tolerance without the need for finished grinding, and the time consuming steps of adhesive coating and elastomer vulcanizing are avoided. The interference fit roller manufacturing process takes seconds rather than hours. Additionally, when the elastomeric coating is damaged, it is easily removed from the shaft simply by slitting the elastomeric tube longitudinally and removing the shaft. The shaft can then be reused to make remanufactured rollers.
Unfortunately, the present inventor has discovered that when such interference fit rollers are employed in contact with photographic processing solution, due to the extreme wetting ability of the solution, some solution leaks between the roller and the shaft. This is undesirable since the trapped solutions can promote corrosion of the shaft and can be transported to a subsequent processing step where it pollutes the subsequent processing solution.
A first solution to this problem that was attempted was to pretreat the shaft with an adhesive. Although this approach solved the fluid leaking problem, it complicated the previously simple interference fit process and reintroduced the problem of environmentally undesirable solvent based adhesives.